Heme in chlorocruorin, the source of its unique green color.
Erythrocruorin (from Greek eruthros "red" + Latin cruor "blood"), and the similar chlorocruorin (from Greek khlōros "green" + Latin cruor "blood"), are large oxygen-carrying hemeproteincomplexes, which have a molecular mass greater than 3.5 million daltons.[1] Both are sometimes called giant hemoglobin or hexagonal bilayer haemoglobin. They are found in many annelids and arthropods (including some insects).[2]